Doctors usually tell their patients not to eat or drink the night before surgery. But there's new evidence that food consumed weeks before an operation could affect how the body responds to the stress of an operation.

A new study found that mice fed a protein-free diet seemed to be protected from complications after surgery. The findings, published in the journal Science Translational Medicine, could give scientists new insight into how to prevent common complications from surgery -  such as heart attacks and strokes - in humans.

Harvard researchers studied two groups of mice, feeding one group a protein-free diet for up to two weeks before surgery, and letting the other group eat normally. The researchers then operated on the mice, using techniques that put their kidneys and livers under added stress.

About 40 percent of the mice who ate normally died after the surgery; all of the mice on the protein-free diet survived.

Previous studies in animals have shown that restricting the diet is one way to help the body cope with stress and stay healthy. Study author James Mitchell, an assistant professor at the Harvard School of Public Health, said he and his team were hoping to find out just which elements of the diet can help or hinder the body's response to stress.

"Surgery, by its nature, is traumatic to the body," Mitchell told ABC News. "With changes to the diet, we're getting the body ready for an acute stress like surgery. If we can do that, the complications might be less severe or there might be fewer complications."

Although the study tested only mice, the trauma their bodies experienced after the surgery is similar to what humans can experience, said Dr. Stavros Memtsoudis, an anesthesiologist at the Hospital for Special Surgery in New York City.

"But the human body is very complex, more complex than mice. How one change affects all other organs is very unknown," Memtsoudis said. "Nevertheless, this opens up a whole new concept that should be investigated. Nutrition is a very nuanced intervention before surgery that should be paid attention to."

The study is among the first to suggest that diet changes in the weeks before surgery can be as important as what patients eat in the days immediately beforehand. Usually, the only advice patients get is not to eat or drink the night before their surgery so the stomach is empty and the risk of choking is decreased.

Mitchell said the next steps will be to test whether protein-free diets will work as well in prepping humans for surgery as they did in mice, which would mean figuring out how long a human would need to lay off hamburgers in order to better respond to the stress of surgery.

"And whether or not people would actually be willing to do it is another question," Mitchell said.